The present invention relates to photosensitizer immunoconjugate compositions and combination therapies for use in cancer related photodynamic treatments and diagnostic methods. Photosensitizer immunoconjugates comprising a photosensitizer conjugated to a tumor-specific and/or tumoricidial antibody and processes for the preparation thereof are described. The use of photosensitizer immunoconjugates (PICs) offers improved photosensitizer delivery specificity for diagnostic and therapeutic applications. Combination therapies to co-localize activated photosensitizer compounds and tumoricidal antibodies in tumor tissues are also described.